[Ancillary studies in the differential diagnosis of epithelial renal cell tumors with granular cells]

Differential diagnosis of renal neoplasms with granular cells may pose difficulties and implications on ontogeny and prognosis. Our aims are to characterize the pattern of immunostaining and to search for a useful diagnosis panel.

We studied with colloidal iron staining (Mowry's modified method) and 22 commonly used immunomarkers 22 conventional carcinomas (CC), 37 chromophobe carcinomas (CPC), 8 oncocytomas (OC), and 7 collecting duct carcinomas (CDC) with granular cells. Cases with not entirely clear diagnosis were excluded.

Colloidal iron staining was diffuse, strong, reticular, and cytoplasmic in 32 CPC cases, the diffuse and strong pattern was not observed in other tumors. The more useful diagnostic panel was cytokeratin 7 (CK7)/CD10/vimentine (vim). The 8 OC were negative for the three antibodies. The most common profile for CC was CK7-/CD10+/vim+, the CPC profile was CK7+/CD10-/vim-, and CDC did not show a particular profile. With these three antibodies specificity was >90% for the differential diagnosis. Adding colloidal iron staining specificity was 100%.

Morphologic features, colloidal iron staining (modified Mowry's method), and immunostaining with CK7/CD10/vim permit the final diagnosis with high specificity. However, a 100% specific marker does not exist at the present time.